Predicate Builder Issue

问题

Imagine I have 2 database tables.. 1 table holds different sports:

|ID|    |Sport|
 1       Baseball
 2       Basketball
 3       Soccer

The second table holds the ID of the Sports table, so a foreign key

Name of Table - TestDB

|ID|    |SportsID|        |Test|
  1          1             test1
  2          3             test2
  3          2             test3
  4          1             test4
  5          2             test5

Now I am using Predicate Builder to allow the user to search through the table in my web application:

[HttpPost]
    public ActionResult allDailySummaries(int? sport, int? sport1)
    {
        List<TestDB> lstTDB = db.TDB.Include(x => x.Sports).ToList();

        var predicate = PredicateBuilder.True<TestDB>();

        if (!string.IsNullOrWhiteSpace(sport.ToString()))
        {
            predicate = predicate.And(x => x.SportsID == sport);   
        }

        if (!string.IsNullOrWhiteSpace(sport1.ToString()))
        {
            predicate = predicate.And(x => x.SportsID == sport).;
        }

        if (predicate.Parameters.Count > 0)
        {
            lstTDB = db.TestDB.AsExpandable().Where(predicate).ToList();
            ViewBag.countSports = lstTDB.Count();
            Session["Paging"] = lstTDB;
            ViewBag.Paging = lstTDB.ToPagedList(page ?? 1, 25);
            return View(lstTDB.ToPagedList(page ?? 1, 25));
        }
        else
        {
            return View(lstTDB.ToPagedList(page ?? 1,25));
        }

I should be able to filter or search by 2 sports.. so if I wanted to search by all records in the TestDB that are either baseball or basketball then that's what I want.. but when I try this, it returns nothing, but if i only search 1 sport it works.

Any help is appreciated.

回答1:

I have solution:

List<int> lstSports = new List<int>();
        if(sport != null)
        {
            lstSports.Add(Convert.ToInt32(sport));
        }
        if (sport1 != null)
        {
            lstSports.Add(Convert.ToInt32(sport1));
        }
        if (lstSports.Count > 0)
        {
            foreach(int i in lstSports)
            {
                if(lstSports.IndexOf(i) == 0)
                {
                    predicate = predicate.And(x => x.SportsID == i);
                }
                else
                {
                    predicate = predicate.Or(x => x.SportsID == i);
                }
            }
        }

来源：https://stackoverflow.com/questions/36624630/predicate-builder-issue